Children's consent and paediatric research: is it appropriate for healthy children to be the decision-makers in clinical research?

AIM

To determine the appropriateness of asking healthy children to make a decision regarding participation in a research study.

METHODS

Participants constituted a group of children taking part in a follow-up to a vaccine study which involved a blood test to look at the persistence of antibodies. Information about the study was given to each child and following venepuncture an oral questionnaire was completed to establish understanding of the vaccine study. Parental views concerning their child's ability to make a decision regarding research participation were also sought.

RESULTS

73 children participated overall. Following venepuncture 59% (n = 43) had grasped some aspect of the reasoning behind venepuncture with 33% (n = 24) unclear. The majority of parents (n = 55) and a substantial number of children (n = 28) believed that the parent should make the decision about study participation, although it is clear that a significant minority of parents thought it is right to involve the child in that process.

CONCLUSION

New guidance about the requirements for informed consent involving children in research is needed, which can respect the autonomy of the child and the role of the parent, while recognising the limited capacity of some children to understand age-appropriate information.

A simplified 4-site economical intradermal post-exposure rabies vaccine regimen: a randomised controlled comparison with standard methods

BACKGROUND

The need for economical rabies post-exposure prophylaxis (PEP) is increasing in developing countries. Implementation of the two currently approved economical intradermal (ID) vaccine regimens is restricted due to confusion over different vaccines, regimens and dosages, lack of confidence in intradermal technique, and pharmaceutical regulations. We therefore compared a simplified 4-site economical PEP regimen with standard methods.

METHODS

Two hundred and fifty-four volunteers were randomly allocated to a single blind controlled trial. Each received purified vero cell rabies vaccine by one of four PEP regimens: the currently accepted 2-site ID; the 8-site regimen using 0.05 ml per ID site; a new 4-site ID regimen (on day 0, approximately 0.1 ml at 4 ID sites, using the whole 0.5 ml ampoule of vaccine; on day 7, 0.1 ml ID at 2 sites and at one site on days 28 and 90); or the standard 5-dose intramuscular regimen. All ID regimens required the same total amount of vaccine, 60% less than the intramuscular method. Neutralising antibody responses were measured five times over a year in 229 people, for whom complete data were available.

FINDINGS

All ID regimens showed similar immunogenicity. The intramuscular regimen gave the lowest geometric mean antibody titres. Using the rapid fluorescent focus inhibition test, some sera had unexpectedly high antibody levels that were not attributable to previous vaccination. The results were confirmed using the fluorescent antibody virus neutralisation method.

CONCLUSIONS

This 4-site PEP regimen proved as immunogenic as current regimens, and has the advantages of requiring fewer clinic visits, being more practicable, and having a wider margin of safety, especially in inexperienced hands, than the 2-site regimen. It is more convenient than the 8-site method, and can be used economically with vaccines formulated in 1.0 or 0.5 ml ampoules. The 4-site regimen now meets all requirements of immunogenicity for PEP and can be introduced without further studies.

TRIAL REGISTRATION

Controlled-Trials.com ISRCTN 30087513.

The magnitude of the antibody and memory B cell responses during priming with a protein-polysaccharide conjugate vaccine in human infants is associated with the persistence of antibody and the intensity of booster response

Rapid waning of anti-polysaccharide bactericidal Ab and vaccine effectiveness is observed following infant immunization with the serogroup C meningococcal (MenC) glycoconjugate vaccine. This is despite the demonstrable presence of immunological memory. Persistence of functional Ab, therefore, appears to be the key determinant of MenC conjugate vaccine effectiveness. Ab persistence is thought to depend in the short term on the survival of plasma cells generated during priming and in the longer term on the production of new Ab secreting cells from memory B cells. In this study, we found a strong association between the level of MenC-specific Ab and the frequency of memory B cells measured at 5 mo of age (1 mo after 3-dose primary immunization with MenC conjugate vaccine), and the persistence of functional Ab at one year of age. These findings suggest that these two parameters are good markers of B cell responses to priming and can be used as predictors of long term humoral immunity induced by glycoconjugate vaccines received in early infancy.

Host genetic factors and vaccine-induced immunity to hepatitis B virus infection

Background

Vaccination against hepatitis B virus infection (HBV) is safe and effective; however, vaccine-induced antibody level wanes over time. Peak vaccine-induced anti-HBs level is directly related to antibody decay, as well as risk of infection and persistent carriage despite vaccination. We investigated the role of host genetic factors in long-term immunity against HBV infection based on peak anti-HBs level and seroconversion to anti-HBc.

Methods

We analyzed 715 SNP across 133 candidate genes in 662 infant vaccinees from The Gambia, assessing peak vaccine-induced anti-HBs level and core antibody (anti-HBc) status, whilst adjusting for covariates. A replication study comprised 43 SNPs in a further 393 individuals.

Results

In our initial screen we found variation in IFNG, MAPK8, and IL10RA to affect peak anti-HBs level (GMTratio of <0.6 or >1.5 and P≤0.001) and lesser associations in other genes. Odds of core-conversion was associated with variation in CD163. A coding change in ITGAL (R719V) with likely functional relevance showed evidence of association with increased peak anti-HBs level in both screens (1st screen: s595_22 GMTratio 1.71, P = 0.013; 2nd screen: s595_22 GMTratio 2.15, P = 0.011).

Conclusion

This is to our knowledge the largest study to date assessing genetic determinants of HBV vaccine-induced immunity. We report on associations with anti-HBs level, which is directly related to durability of antibody level and predictive of vaccine efficacy long-term. A coding change in ITGAL, which plays a central role in immune cell interaction, was shown to exert beneficial effects on induction of peak antibody level in response to HBV vaccination. Variation in this gene does not appear to have been studied in relation to immune responses to viral or vaccine challenges previously. Our findings suggest that genetic variation in loci other than the HLA region affect immunity induced by HBV vaccination.

Haemophilus influenzae type b vaccine failure in children is associated with inadequate production of high-quality antibody

BACKGROUND

Despite the excellent immunogenicity of Haemophilus influenzae type b (Hib) conjugate vaccines, breakthrough cases of Hib disease still affect a small proportion of vaccinated children in the United Kingdom. We performed a retrospective study to compare the avidity of antibody directed against the Hib polysaccharide capsule (PRP) in children who experienced Hib vaccine failure in the United Kingdom among 3 historical cohorts and with age-matched healthy control subjects.

METHODS

Serum samples from vaccinated children with invasive Hib disease were collected beginning in 1992 as part of enhanced surveillance for Hib disease following vaccine introduction. A total of 251 children who experienced Hib vaccine failure were identified from 3 historical cohorts (1992-1995, 1996-1999, and 2000-2003). The anti-PRP antibody concentration and avidity from healthy age-matched control subjects was obtained for the 3 contemporary time points (1995, 1999, and 2002). Serum anti-PRP antibody concentration was measured in each of the samples using a standard Hib ELISA, and antibody avidity was determined using thiocyanate elution.

RESULTS

Within the first 60 days after disease onset, there was no change in the anti-PRP antibody avidity, and there was no statistically significant difference in the geometric mean Hib antibody avidity over the 3 study periods. However, the children who experienced Hib vaccine failure had significantly lower Hib antibody avidity than did healthy control subjects, despite a marked antibody response following infection.

CONCLUSIONS

Children who experience Hib disease despite vaccination appear to have a defect in immunological priming, leading to a qualitative difference in Hib-specific memory B cells. Low anti-PRP antibody avidity decreases the functional activity of anti-PRP antibody in the sera of these children experiencing vaccine failure, leading to disease susceptibility.

Immunogenicity of a tetravalent meningococcal glycoconjugate vaccine in infants: a randomized controlled trial

CONTEXT

Immunization with a meningococcal tetravalent (serogroup ACWY) glycoconjugate vaccine is recommended for all US adolescents. However, the currently licensed vaccine is poorly immunogenic in infancy, when the highest rates of disease are observed.

OBJECTIVE

To determine the immunogenicity of a novel tetravalent CRM(197)-conjugated meningococcal vaccine (MenACWY) in infants.

DESIGN, SETTING, AND PARTICIPANTS

Randomized, open-label, controlled study of 225 UK and 196 Canadian 2-month-olds from August 2004 to September 2006.

INTERVENTION

UK infants received a primary course of MenACWY (at 2, 3, and 4 months or 2 and 4 months) or Neisseria meningitidis serogroup C monovalent meningococcal glycoconjugate vaccine (MenC) (at 2 and 4 months). All received MenACWY at 12 months. Canadian infants received MenACWY at 2, 4, and 6 months or 2 and 4 months; at 12 months they received MenACWY, a plain tetravalent polysaccharide vaccine, or no vaccine.

MAIN OUTCOME MEASURE

Percentage of infants with a human complement serum bactericidal activity (hSBA) titer >or=1:4 after a primary course of MenACWY and after a 12-month booster. Safety and reactogenicity of MenACWY were also assessed.

RESULTS

According to the prespecified per-protocol analysis, the percentages (95% CIs) of MenACWY 2-, 3-, and 4-month recipients with hSBA titers >or=1:4 after primary immunization were serogroup A, 93% (84%-98%); C, 96% (89%-99%); W-135, 97% (90%-100%); and Y, 94% (86%-98%). With a post hoc intention-to-treat analysis with imputed values for missing data, these values were unchanged for serogroups C and Y; for serogroup A, values were 92% (84%-97%), and for W-135, 97% (91%-99%). For the per-protocol analysis of MenACWY 2-, 4-, and 6-month recipients, the percentages (95% CIs) of responders were A, 81% (71%-89%); C, 98% (92%-100%); W-135, 99% (93%-100%); and Y, 98% (92%-100%). With the imputed value analysis, these values were A, 83% (74%-89%); C, 98% (93%-99%); W-135, 99% (94%-100%); and Y, 98% (92%-99%). At least 84% of MenACWY 2- and 4-month recipients achieved hSBA titers >or=1:4 for serogroups C, W-135, and Y after primary immunization, as did at least 60% for serogroup A (per-protocol and imputation analysis). At least 95% of primary and booster MenACWY recipients achieved hSBA titers >or=1:4 for serogroups C, W-135, and Y at 13 months, as did at least 84% for serogroup A (per-protocol and imputation analysis). During the primary immunization course, postimmunization pain on leg movement was observed in 2% of UK MenACWY 2- and 4-month recipients and 4% of MenC 2- and 4-month recipients; a temperature of 38 degrees C or greater was observed in 4% and 2% in these groups, respectively.

CONCLUSION

MenACWY is well tolerated and immunogenic in infancy. Trial Registration clinicaltrials.gov Identifier: NCT00262002.

Children's participation in vaccine research: parents' views

AIM

Vaccine studies that evaluate the persistence of protection following immunisation require subjects to continue participation in a research protocol over many years. As parents' attitudes and opinions may change over time, and with experience of research, it is important to consider the factors influencing parents' decision-making about their child's continued participation in such prolonged vaccine studies.

METHOD

Parental views about participation of their child in a one-year follow-up vaccine study were explored by means of a self-administered questionnaire. Of the 254 eligible parents, 187 took part (74 per cent).

RESULTS

Parents who provided consent were more likely to agree that having a home visit to take blood was very helpful (p=0.005) and that information obtained during the earlier part of the study influenced their decision to take part in a follow-up study (p<0.0001). Parents who did not consent to their child's participation were more likely to report the presence of personal reasons as a variable influencing their decision (p<0.0001).

CONCLUSIONS

The relationship between study staff and parents is the cornerstone for success in performing studies involving vaccines and children. Provision of clear study information (oral and written) and offering the convenience of home visits are important in retaining participants in paediatric vaccine trials.

Uptake and acceptability of influenza vaccination in day nursery children

Preschoolers play an important role in the transmission of influenza, and suffer significant morbidity. Paediatric vaccination could prevent serious outcomes and offer broader societal benefits. This study explored parental views on influenza and paediatric vaccination and determined the uptake of a nursery-based vaccination programme for infants aged 6-23 months. Children were offered two doses of inactivated vaccine in 2004/05, and a single dose at the start of the 2005/06 season. An uptake rate of 11% (60/535) was achieved with 83% (50/60) of participants completing the programme. Semi-structured interviews were conducted with 10 parents. Thematic analysis of the data informed the development of a questionnaire. This was distributed to 650 parents, with children aged 6-30 months attending one of the 18 supporting nurseries. A response rate of 13% (83/650) was achieved. The low uptake rate achieved in the programme and findings from the interviews/questionnaire suggest parents were not convinced about the seriousness of paediatric influenza. Indeed, over two-thirds (55/81) questioned the necessity for an annual vaccination. Parents found it difficult to differentiate influenza from other respiratory illnesses, and expressed concerns about the need for annual injections and vaccine safety. Paediatric vaccination to increase herd immunity was held in balance with the notion that children should only be vaccinated if they are the main beneficiaries. Parental education on the burden of childhood influenza, on the direct benefits of influenza vaccination, and on indirect benefits to society is a necessity for a successful paediatric vaccination programme.

Hepatitis B vaccination

The BMA adds its voice to the call for universal childhood immunisation in the UK

Haplotypic diversity in human CEACAM genes: effects on susceptibility to meningococcal disease

Adhesion between the opacity-associated adhesin (Opa) proteins of Neisseria meningitidis and human carcino-embryonic antigen cell adhesion molecule (CEACAM) proteins is an important stage in the pathogenesis of meningococcal disease, a globally important bacterial infection. Most disease is caused by a small number of meningococcal genotypes known as hyperinvasive lineages. As these are also carried asymptomatically, acquisition of them alone cannot explain why only some hosts develop meningococcal disease. Our aim was to determine whether genetic diversity in CEACAM is associated with susceptibility to meningococcal disease. Frequency distributions of alleles, genotypes and haplotypes were compared in four CEACAM genes in 384 case samples and 190 controls. Linkage disequilibrium among polymorphic sites, haplotype structures and relationships were also analysed. A number of polymorphisms were observed in CEACAM genes but the diversity of CEACAM1, to which most Opa proteins bind, was lower, and a small number of high-frequency haplotypes were detected. Dose-dependent associations of three CEACAM haplotypes with meningococcal disease were observed, with the effect of carrying these haplotypes amplified in homozygous individuals. Two haplotypes were protective while one haplotype in CEACAM6 was associated with a twofold increase in disease susceptibility. These data imply that human CEACAM may be one determinant of human susceptibility to meningococcal disease.

Meningococcal A, C, Y and W-135 polysaccharide-protein conjugate vaccines

Serogroup C meningococcal conjugate vaccines, first launched in the UK in 1999, have been used successfully in Australia, Canada and several other European countries. Combination conjugate vaccines, containing more than one meningococcal polysaccharide, have been developed to broaden protection against the disease. A tetravalent meningococcal A, C, Y and W-135 conjugate vaccine was licensed for use in 11-55 year old adolescents and adults in the US in January 2005, and subsequently also in 2-11 year old children in Canada in May 2006. This article discusses the different glycoconjugate meningococcal vaccines which have been developed and the potential for their use to control disease caused by serogroups A, C, Y and W-135 of Neisseria meningitidis.

Reconsideration of the use of meningococcal polysaccharide vaccine

In 2005, a quadrivalent meningococcal conjugate vaccine was licensed in the United States for persons aged 11-55 years of age. For children aged 2-10 years with underlying diseases associated with increased risk of meningococcal disease, unconjugated meningococcal polysaccharide (MPS) vaccination is still recommended. This article reviews the increasing evidence that MPS vaccination impairs serum anticapsular antibody responses to subsequent injections of MPS or meningococcal conjugate vaccines (antibody hyporesponsiveness). Administering MPS as a probe to assess conjugate vaccine-induced immunologic memory also can extinguish subsequent memory anticapsular antibody responses, whereas conjugate vaccination regenerates memory B cells. Whether induction of antibody hyporesponsiveness or loss of immunologic memory increase the risk of acquiring meningococcal disease remains speculative. However, for children at increased risk of meningococcal disease, immunization with meningococcal quadrivalent conjugate vaccine off-label instead of MPS vaccine should be considered. Requirements for licensure of new glycoconjugate vaccines that include performing comparative clinical trials to demonstrate noninferiority with MPS vaccine, or use of a MPS challenge to assess conjugate-induced immunologic memory also should be modified because there are safer approaches for obtaining the same information.

Childhood immunisation: what is the future?

Improved immunisation programmes and the development of new vaccines provide unprecedented opportunities to improve and sustain the health of our children. There are major challenges ahead in communicating the benefits of immunisation to all populations and in delivering vaccines to those in greatest need. In this review on immunisation, I have asked international opinion leaders to comment on the present and the future of immunisation to provide signposts for the narrative.

A randomized study comparing the safety and immunogenicity of a conjugate vaccine combination containing meningococcal group C and pneumococcal capsular polysaccharide—CRM197 with a meningococcal group C conjugate vaccine in healthy infants: Challenge phase

BACKGROUND

A combination nonavalent pneumococcal-group C meningococcal conjugate vaccine (Pnc9-MenC) was previously found to be safe and immunogenic when administered to infants at 2, 3 and 4 months. This study describes the persistence of immunity at 12 months of age and the immunologic response to a challenge dose of either meningococcal polysaccharide vaccine (Meningivac A+C; MnA+C), or MenC.

METHODS

A phase II, randomized, controlled trial of healthy infants. Subjects were given Pnc9-MenC or MenC vaccine at 2, 3 and 4 months of age and then challenged with either MenC or MnA+C. Group C meningococcal immunogenicity was measured by serum bactericidal assay (SBA) and an enzyme-linked immunosorbent assay (ELISA) adapted to measure antibody avidity pre- and post-challenge.

RESULTS

The MenC vaccine was more immunogenic than the Pnc9-MenC vaccine in persistence of serogroup C meningococcal polysaccharide antibodies at 12 months of age. Post-challenge at 13 months there were significant differences between the four groups in the induction of serogroup C meningococcal polysaccharide antibodies. The responses to MenC/MenC were significantly higher than in the other groups (p<0.001) and the responses to Pnc9-MenC/MnA+C were significantly lower than in the other groups (p<0.001). There was no difference between the four groups in the proportions with geometric mean concentrations (GMC) greater than 2 microg/ml (p=0.18) or with SBA titres greater than or equal to the protective level of 1:8 (p=0.89). The SBA geometric mean ratio (GMR) between pre- and post-challenge was higher in the groups challenged with MenC than those challenged with MnA+C. Antibody avidity increased over time.

CONCLUSION

We have shown that Pnc9-MenC primes effectively for immunological memory. At 13 months of age the highest immune responses were seen in the subjects primed and challenged with MenC alone. However, all groups achieved the threshold levels required for protection.

Emergency management of meningococcal disease: eight years on

Application of the new edition of the meningococcal treatment algorithm may help in the early management of critically ill patients

The role familiarity with science and medicine plays in parents' decision making about enrolling a child in vaccine research

Parental consent to children's participation in vaccine research has resulted in the licensure of essential vaccines. Recruitment to this type of research is typically difficult, however, and many parents decline. In this study, the authors interviewed parents about their decision for or against enrolling their child in a vaccine study. The data analysis suggests that parents' ability to evaluate a vaccine study depends on how attuned they are with science and medicine, either professionally or as consumers of health services. Familiarity does not predispose parents to enrolling their child in research; rather, it is a predictor of parents' confidence in their decision making. Many parents were motivated by altruism and trust, which, if uninformed, can leave the parents prone to exploitation. It is vital to ensure that parents are confident in their judgment of a study and its potential benefit to their child and society.

Immunogenicity and induction of immunological memory of the heptavalent pneumococcal conjugate vaccine in preterm UK infants

Data on the immunogenicity and memory induction of pneumococcal conjugate vaccines in very preterm infants is limited. We vaccinated 69 full term and 68 preterm infants (median gestational age (GA) 30 weeks) with a 7-valent pneumococcal conjugate vaccine (PCV7) at 2/3/4 months of age, followed by a plain polysaccharide booster at 12 months of age. IgG-GMC (ELISA) was significantly lower in preterm infants to six vaccine serotypes (ST) at 2 months and 5 months of age, to five ST at 12 months of age and to three ST at 13 months of age. A significantly lower proportion of preterm infants achieved IgG levels>or=0.35 microg/ml to ST 4, 6B and 9V at 5 months and to ST 4, 6B, 18C, 19F and 23F at 12 months of age. Fold rises following the polysaccharide booster were comparable to those of term infants. At least 93% of both cohorts achieved IgG>or=0.35 microg/ml to all STs following booster vaccination. Pneumococcal conjugate vaccine at an accelerated schedule of 2/3/4 months of age is likely to provide protection against pneumococcal disease for preterm infants. Antibody concentrations wane over the first year of life in both preterm and term infants and booster vaccination is therefore likely to be important.

New combination vaccines still need a boost

Perspective on the paper by Kitchin et al (see page XXX)

Serogroup C Meningococcal Glycoconjugate Vaccine in Adolescents: Persistence of Bactericidal Antibodies and Kinetics of the Immune Response to a Booster Vaccine More Than 3 Years after Immunization

BACKGROUND

The persistence of protection from meningococcal disease following immunization with serogroup C meningococcal (MenC) glycoconjugate vaccines in infancy is short-lived. The duration of protective immunity afforded by these vaccines in other at-risk age groups (i.e., adolescents and young adults) is not known. We evaluated the persistence of bactericidal antibodies following immunization with a MenC glycoconjugate vaccine (MenCV) in adolescents and the kinetics of immune response to a meningococcal AC plain polysaccharide vaccine (MenPS) challenge or a repeat dose of MenCV.

METHODS

We conducted a randomized comparative trial of 274 healthy 13-15-year-olds from whom a total of 4 blood samples were obtained (prior to administration of a dose of MenPS or MenCV, again on 2 further occasions at varying times from days 2-7 after vaccination, and finally on day 28 after vaccination. The correlate of protection was a serum bactericidal assay titer > or = 8 (with a serum bactericidal assay using human complement).

RESULTS

A serum bactericidal assay using human complement titer > or = 8 was observed in 75% of participants at baseline (mean age, 14.5 years; mean time since routine MenCV vaccination, 3.7 years). No increase in serum bactericidal assay geometric mean titers was detected until day 5 after administration of MenPS. Geometric mean titers following administration of MenCV were significantly higher than those observed following administration of MenPS, at days 5, 7, and 28.

CONCLUSIONS

This study showed sustained levels of bactericidal antibodies for at least 3 years after immunization of adolescents with MenCV. After challenge of immunized adolescents with MenPS, there was no increase in serum bactericidal assay observed until day 5 after vaccination, indicating that immunological memory may be too slow to generate protection against this potentially rapidly invasive organism.